Catheter assemblies, and particularly catheter assemblies for use in hemodialysis, are known that have one, two or more lumens extending from a distal end to a proximal end, where the distal end is placed in a blood vessel of a patient, such as the jugular vein, with the proximal end extending from the patient for each lumen to be connected to a respective conduit of a hemodialysis machine. Customarily, each lumen of the catheter assembly is first connected to a respective extension tube within a hub body, and the extension tube is terminated in a luer connector to facilitate connection with and disconnection from the conduit of the hemodialysis machine and commonly the extension tube has disposed therealong a clamp, such as a Roberts clamp, for temporarily closing the conduit when necessary. Implanted catheter assemblies are connected to medical apparatus such as hemodialysis apparatus through the luer connectors, and then disconnected therefrom, all through many cycles; such connection and disconnection involves the catheter assembly undergoing many cycles of stress and strain especially focused at the proximal end where the catheter proximal end enters the hub which connects the catheter lumens to respective extension tubes, or where a single lumen catheter enters its luer connector directly instead of via a hub and extension tube.
It is desired to provide an assurance against occluding or kinking of the catheter lumens, as well as greater strength, at the connection of the catheter and the hub, or at the connection of a single lumen catheter luer connection where no hub is utilized.
Certain catheter assemblies, termed PICC catheters (for peripherally inserted central catheters), are implanted through a vessel entry on an arm of the patient, known as axillary placement. But, usually, the catheter assembly is secured to the torso of the patient in a manner to prevent any dislocation of the distal tips of the catheter lumens from any movement along the vessel after initial placement at the catheterization site. This manner of securement is usually accomplished by a process termed tunneling, in which the proximal portion of the catheter assembly outside of the vessel is tunneled subcutaneously near the vessel entry site, typically beneath the clavicle of the patient, whereafter the hub is sutured or otherwise secured to the patient. By this process, during the connection with and disconnection from the hemodialysis machine of the extension tubes, there is no stress or strain passed to the distal end of the catheter assembly that might tend to dislodge the distal lumen tips from the desired location along the vessel.
The orientation of the tunneled portion of the catheter assembly is not axially aligned with the distal portion of the catheter assembly and in fact a relatively sharp bend may be made in the catheter assembly distally of the tunneled portion during placement.
Catheters are conventionally produced in various sizes depending on desired uses, and their outer diameters are measured in units termed “french” or “F”, with one F equaling 0.013 inches or 0.32 millimeters. The largest sized catheters utilized for vascular placement may have an outer diameter of about 17 F, and range to smaller sizes. Diameters of 5 F are the smallest sized dual-lumen catheters that are presently preferred in that they present little difficulty with insertion therethrough of small wires or stylets, or that have sufficient strength and thus less kink susceptibility. Even smaller sized catheters are known, however (4 F or less), such as are used with small adolescents and adults. When the catheter outer diameter is almost the same size as the inner diameter of the vessel within which it is implanted, certain problems are associated with catheters after they are vascularly in a patient; for example, development of phlebitis and thrombosis is known in such situations.
It is desired to provide a catheter with a very small outer diameter, especially a dual lumen catheter, thereby minimizing the tendency of phlebitis or thrombosis or the like, to develop. Such a small diameter catheter is disclosed in U.S. Patent Publication No. US 2006/0206094 A1, which provides a catheter assembly wherein the catheter outer diameter is enlarged for at least some of its length proximate the proximal end adjacent the hub, relative to the remainder of the catheter extending to the distal end. The inner diameter of the lumen or lumens remains constant; in a dual-lumen catheter, the inner septum wall between the lumens may also increase in thickness. A very small diameter dual lumen catheter (2.6 F) disclosed in the application provides two circular lumens each with a very small diameter of about 0.011 in (0.028 mm), sufficiently large for an 0.009 inch guide wire (0.23 mm) or 18 GA, and which is less likely to induce phlebitis, thrombosis or the like after implantation. This very small diameter catheter also benefits from an enlarged proximal end diameter, for resistance to occlusion and kinking. The use of stylets with catheters provides rigidity to the catheter during insertion of the catheter into the patient. The catheter could also be inserted over a guide wire, where the guide wire too would provide rigidity and guidance into and through the vasculature.
It is desired to provide a small diameter catheter suitable for use with stylets or guide wires that provide a sufficiently great level of rigidity to the small diameter catheter during patient placement.